NASA Quest > Aerospace Team Online

PART 1: Upcoming Chat
PART 2: Prizes for Early Contest Entries
PART 3: Colorful 3D Animation
PART 4: Pressure Sensitive Paint Testing and Tennis Ball Research
PART 5: Subscribing & Unsubscribing: How to do it

Tuesday, March 31, 10:00 a.m.- 11:00 a.m. Pacific Time: Andrew Hahn, Conceptual Aircraft Designer Andrew designs aircraft concepts. He uses physics every day in his job. Registration information is at http://quest.arc.nasa.gov/aero/chats/#chatting Read his biography prior to joining this chat. http://quest.arc.nasa.gov/aero/team/hahn.html Thursday, April 2, 1998 11:00 a.m.- 12:00 p.m. Pacific Time: Rabi Mehta, Senior Research Scientist, Rabi is an expert in the aerodynamics of sports balls from cricket balls to golf balls. This chat will also cover the topic of a new air pressure measurement technique for wind tunnel tests! Read Rabi's journal at http://quest.arc.nasa.gov/aero/team/fjournals/mehta/ Registration information is at http://quest.arc.nasa.gov/aero/chats/#chatting Read his biography prior to joining this chat. http://quest.arc.nasa.gov/aero/team/rabi.html Tuesday, April 14, 10:00 a.m.- 11:00 a.m. Pacific Time: Dave Korsmeyer, Senior Project Scientist Dave is a project manager who develops advanced information technology and systems like near real time remote access to wind tunnel data. Registration information is at http://quest.arc.nasa.gov/aero/chats/#chatting Read his biography prior to joining this chat. http://quest.arc.nasa.gov/aero/team/korsmeyer.html Thursday, April 30, 1:00 p.m.- 2:00 p.m. Pacific Time: Estela Hernandez, Flight Simulation Engineer Estela is a flight simulation engineer. She uses math to build computer models that simulate flying airplanes. This chat will be in English and Spanish. Registration information is at http://quest.arc.nasa.gov/aero/chats/#chatting Read her biography prior to joining this chat. http://quest.arc.nasa.gov/aero/team/hernandez.html

As you know we are holding two contests: "Draw a Picture of an Airplane" and "Write an Essay Describing the Airplane You Would Like to Design", http://quest.arc.nasa.gov/aero/events/index.html An early bird prize will be awarded to entries received by March 30, 1998. So far no one has earned an early bird prize.

February 13, 1998

Hi. This will be my first journal report. I'm an engineer here at NASA Ames. I work for a contractor, called Sterling Software, which provides computer services to the government. The people who work for my company do business on site at Ames and perform a variety of jobs, including computer networking, systems administration, procurement, and software development. We typically use government furnished equipment. The company has been a very important partner in the development of the vast computing capability present at Ames. Such a capability is necessary in order to maintain excellence in aerospace research here. My job involves software development and application. I have a bachelor's degree in mechanical engineering from the University of California at Berkeley. I received my degree a little over ten years ago and have been working at Ames for all of my career. Currently, I support a part of NASA Ames, known as the Military Technology Branch. Their recent accomplishments involve the successful testing of the X-36 Tailess Jet Fighter down at NASA Dryden Research Center in the Mojave Desert. The branch played a key role in its design. I've never seen the plane directly myself, but some of my work supported its development. This is sometimes typical of many jobs where you work on a piece and don't get to see the whole picture until much later. This is often done for reasons involving security. Only a few high level engineers will understand fully about such a project while it is being carried out. I work in a field called CFD, or Computational Fluid Dynamics. It involves the application of computer codes on high speed computers in order to analyze fluid flow around and/or through aircraft. I began out of college working on Fortran programs at Ames. Much of it was minor, involving short programs for analyzing data. I got started in CFD at about two years into my career, running codes to analyze inlets for hypersonic air vehicles which travel at Mach 5 to 18. I'd work with engineers who are much more experienced than I, and I'd learn from them. I'd also read technical papers and books, and learn by doing. In this manner, during my career, I've developed a knowledge of and the ability to write and modify the analytical computer codes necessary to solve CFD problems. What I like best about my situation is that more time is given me to learn and experiment than in most places. CFD application involves two major areas. The first is grid generation, which is the production of surface and off- surface 3D grids in order to model the airplane body and surrounding area. (Think of a wireframe model of an airplane, then grow out many more wire frames from the surface of the airplane, each a little larger than the previous one.) The second is flow solver application, where air flow is modeled mathematically. (Make the inner wireframe model a solid surface, and imagine a computer blowing air over the entire collection of wireframe models. Take air pressure, speed, and energy readings at the points where the wireframes intersect. That is basically CFD.) A typical day for me would be to first check email. I get only a few messages a day usually. Maybe my boss will remind me to fill out my timesheet, or someone will ask me for advice about a computer program that I wrote, or a colleague might want to make a comment about the NFL playoffs. We work hard, but discussions are not all business. It's generally a relaxed atmosphere here. I would then walk to another building to check on some computer jobs that I submitted the previous day to run overnight. Much of a CFDer's work involves trial and error, so that if something that I tried had worked, I'd be pleasantly surprised. Typically, analyzing an airplane with CFD takes much work ahead of time in order to develop a good strategy, and to make sure that no problems are encountered. I might write programs or modify existing ones to ensure that things go right. Sometimes it takes weeks to get an answer from the computer. During the process, I'll take a look at the airplane and flowfield on a computer workstation to make sure things are working. This is often fun, and involves looking at (rotating, translating, zooming in) colorful 3D animations in order to see flow features. Boundary layers, wakes, vorticies usually produce colorful patterns which can be easily seen. It's rather beautiful to look at and usually gets me thinking about how to do things better. Much of an engineer's job is to improve on something that's already good (not to mention something that's not so good). Looking at things closely helps a person to get inspired and develop better ways of doing things. It's usually very satisfying to see the final result after one's ideas are put to work. Anyway, that's it for now. I'm heading off to another building. We've been getting a lot of rain recently, but it's Friday, and it looks sunny outside.

March 24, 1998 We just completed a wind tunnel test on a 40% commercial van model in the NASA Ames 7 X 10 foot low-speed wind tunnel. The main goal of the test was to identify noise sources --- a lot of the noise heard on the inside of a vehicle is aerodynamic noise generated by wind flow patterns around the vehicle. On this particular test, an array of microphones was installed on the test section side wall to measure the noise levels. This part of the test was run by another research group. The main task of our group was to measure the surface pressure distribution on certain parts of the van. The pressures on the surface are determined by the flow patterns and they give a good idea of the locations and strengths of the noise sources. The surface pressures on the van model were measured using a relatively new measurement technique which involves the use of a special "pressure sensitive" paint. The paint was excited by a special light source and by measuring the intensity of the emitted light, we determined the pressures on the model. Two high grade scientific CCD cameras were used to image the surface and the data were then processed on work stations. We obtained data over a speed range of 100 to 150 mph --- the relatively high speeds are needed to compensate for the fact that the model is scaled down. We investigated the effects of side mirrors and rain gutters on the pressure distributions. The preliminary results look very promising and we are particularly excited because this is the first time that this measurement technique has been used at such low speeds --- the technique typically works better at higher speeds (transonic to supersonic). The data from this test will hopefully help in designing quieter vehicles in the future. For more details of this new measurement technique and some sample data, check out the following website: http://sisko1.arc.nasa.gov/psp/homepage.html As part of my continued interest and research in sportsball aerodynamics, I am currently participating in a project on tennis balls. This project is mainly involved with the aerodynamics and dynamics of the tennis ball, although some studies also include the bio-mechanics of players in action. High-speed videos have been shot at professional tournaments generating data on the speed and spin rates of the ball at various stages of its trajectory. The bounce properties of the various balls used in Grand Slam events on the different surfaces (grass, clay, hardcourt) are also being investigated. A computational program is underway which we hope will eventually be able to predict the flight of a ball, given the initial conditions. A wind tunnel test program is also planned to study the flow features over a tennis ball and to measure the aerodynamic forces acting on the ball. Check out the following website for complete and regularly updated details of this research program: http://wings.ucdavis.edu/Tennis For the forthcoming web chat scheduled for April 2, 1998 I will be happy to answer questions on both topics (pressure sensitive paint and tennis ball aerodynamics). I have also studied the aerodynamics of other sportsballs (e.g. cricket, baseball and golf) and questions on these topics are also welcome.

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